more transpiler docs improvements (#11300)

* more transpiler docs improvements

* Update qiskit/transpiler/__init__.py

Co-authored-by: Matthew Treinish <mtreinish@kortar.org>

* use double ticks and remove extra line of code

---------

Co-authored-by: Matthew Treinish <mtreinish@kortar.org>

Author: kevinsung

qiskit/transpiler/__init__.py

@@ -105,40 +105,45 @@
 
 .. code-block:: python
 
-    from qiskit.circuit.library import XGate, HGate, RXGate, PhaseGate, TGate, TdgGate
+    import numpy as np
+    from qiskit.circuit.library import HGate, PhaseGate, RXGate, TdgGate, TGate, XGate
     from qiskit.transpiler import PassManager
-    from qiskit.transpiler.passes import ALAPScheduleAnalysis, PadDynamicalDecoupling
-    from qiskit.transpiler.passes import CXCancellation, InverseCancellation
+    from qiskit.transpiler.passes import (
+        ALAPScheduleAnalysis,
+        CXCancellation,
+        InverseCancellation,
+        PadDynamicalDecoupling,
+    )
 
-    backend_durations = backend.target.durations()
     dd_sequence = [XGate(), XGate()]
-    scheduling_pm = PassManager([
-        ALAPScheduleAnalysis(backend_durations),
-        PadDynamicalDecoupling(backend_durations, dd_sequence),
-    ])
+    scheduling_pm = PassManager(
+        [
+            ALAPScheduleAnalysis(target=backend.target),
+            PadDynamicalDecoupling(target=backend.target, dd_sequence=dd_sequence),
+        ]
+    )
     inverse_gate_list = [
         HGate(),
         (RXGate(np.pi / 4), RXGate(-np.pi / 4)),
         (PhaseGate(np.pi / 4), PhaseGate(-np.pi / 4)),
         (TGate(), TdgGate()),
-
-    ])
-    logical_opt = PassManager([
-        CXCancellation(),
-        InverseCancellation([HGate(), (RXGate(np.pi / 4), RXGate(-np.pi / 4))
-    ])
+    ]
+    logical_opt = PassManager(
+        [
+            CXCancellation(),
+            InverseCancellation(inverse_gate_list),
+        ]
+    )
 
 
     # Add pre-layout stage to run extra logical optimization
     pass_manager.pre_layout = logical_opt
     # Set scheduling stage to custom pass manager
     pass_manager.scheduling = scheduling_pm
 
-
-Then when :meth:`~.StagedPassManager.run` is called on ``pass_manager`` the
-``logical_opt`` :class:`~.PassManager` will be called prior to the ``layout`` stage
-and for the ``scheduling`` stage our custom :class:`~.PassManager`
-``scheduling_pm`` will be used.
+Now, when the staged pass manager is run via the :meth:`~.StagedPassManager.run` method,
+the ``logical_opt`` pass manager will be called before the ``layout`` stage, and the
+``scheduling_pm`` pass manager will be used for the ``scheduling`` stage instead of the default.
 
 Custom Pass Managers
 ====================